The Micro-Electro-Mechanical Systems (MEMS) technology is directed to the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate using microfabrication technology. While the electronics is fabricated using integrated circuit process sequences, the micromechanical components are fabricated using processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices.
MEMS combine silicon-based microelectronics with micromachining technology, making it possible to realize complete systems-on-a-chip. MEMS is a technology allowing the development of smart products, and to add perception and control capabilities of microsensors and microactuators to the computational ability of microelectronics.
A particular type of MEMS is a microelectromechanical system microphone, which is also called a microphone chip or silicon microphone. The pressure-sensitive diaphragm of such a MEMS micophone is etched directly into a silicon chip by MEMS techniques. MEMS microphones are usually variants of the condenser microphone design. In many cases MEMS microphones have built in analog-to-digital converter circuits on the same chip making the chip a digital microphone, which can be integrated with modern digital products such as mobile phones.
MEMS that convert sound into electrical signals, in particular MEMS microphones need to be tested for their correct function. According to the prior art as described e.g. in DE 10 2008 015 916 A, this is done by irradiating sound at the MEMS, with terminals of the MEMS being connected to test electronics. The sound is produced using piezo elements to generate desired frequencies in a sound space. The sound space is chosen such that its largest free length, for example its diagonal extension, is smaller than half of the wavelength of the sound waves generated with the highest frequency. As an example, in case of sound tests with frequencies up to 20 kHz, 10 kHz, and 8 kHz, the disclosure of this prior art document requires a maximum of the free length to be 0.86 cm, 1.7 cm and 2.1 cm, respectively, i.e., the MEMS are tested in the near field region. The sound space needs to be isolated to the outside using O-rings such that standing waves can be generated.
However, this method and this device of the prior art have the disadvantage that the placement of the MEMS is time consuming and difficult to handle.